Well, as always, we have achieved complete unanimity of thought on the topic under discussion... (grin). Sean's comments are valid: there is no "need" to have two subs, unless your personal criteria include getting the best performance from your system (sorry, Sean, no attack meant). Gasman has identified some of the reasons favoring two subs in a system, to which I would add that using only one sub requires that you sum the left and right channel inputs, thereby losing phase and channel-related information that can be important in creating a cohesive sonic picture. (This may not be a major concern if you only want to reproduce low frequency sound effects from DVD's, but will definitely be an important consideration if you want good music fidelity.)
When I began playing seriously with subwoofers in my system about two years ago, I started with a single sub of modest quality. When I added the second sub to make a stereo pair, I was surprised how much the overall sound improved for music as well as HT. Last fall, I sold the two subs I had and replaced them with Vandersteen 2Wq subs, and the overall musicality of the system went up dramatically.
Richard Vandersteen has made the comment in several interviews that subwoofers do more than just juice up the deep bass. If the sub and crossover are properly designed to integrate well with the main speakers, the main speakers will have less -- often significantly less -- harmonic and intermodulation distortion because they are not trying to reproduce the low frequency range. The result is clearer, better focused upper bass and lower midrange reproduction, which yields more transparent, detailed sound. My own experience with the two Vandy subs certainly proved this to be true.
Hence, if you are looking for the best musical performance from your system, I urge you to think about eventually having two subs. If money is tight, start with one sub now, and add another later. However, don't get cheap subs that are intended mainly for HT LFE reproduction. There are a number of subs that do a fine job with music that aren't terribly expensive -- see the Audiogon archives for the numerous threads of recommended subwoofers for ideas.
When I began playing seriously with subwoofers in my system about two years ago, I started with a single sub of modest quality. When I added the second sub to make a stereo pair, I was surprised how much the overall sound improved for music as well as HT. Last fall, I sold the two subs I had and replaced them with Vandersteen 2Wq subs, and the overall musicality of the system went up dramatically.
Richard Vandersteen has made the comment in several interviews that subwoofers do more than just juice up the deep bass. If the sub and crossover are properly designed to integrate well with the main speakers, the main speakers will have less -- often significantly less -- harmonic and intermodulation distortion because they are not trying to reproduce the low frequency range. The result is clearer, better focused upper bass and lower midrange reproduction, which yields more transparent, detailed sound. My own experience with the two Vandy subs certainly proved this to be true.
Hence, if you are looking for the best musical performance from your system, I urge you to think about eventually having two subs. If money is tight, start with one sub now, and add another later. However, don't get cheap subs that are intended mainly for HT LFE reproduction. There are a number of subs that do a fine job with music that aren't terribly expensive -- see the Audiogon archives for the numerous threads of recommended subwoofers for ideas.